The multidimensional nature of pathologic vocal quality

Abstract

Although the terms "breathy" and "rough" are frequently applied to pathological voices, widely accepted definitions are not available and the relationship between these qualities is not understood. To investigate these matters, expert listeners judged the dissimilarity of pathological voices with respect to breathiness and roughness. A second group of listeners rated the voices on unidimensional scales for the same qualities. Multidimensional scaling analyses suggested that breathiness and roughness are related, multidimensional constructs. Unidimensional ratings of both breathiness and roughness were necessary to describe patterns of similarity with respect to either quality. Listeners differed in the relative importance given to different aspects of voice quality, particularly when judging roughness. The presence of roughness in a voice did not appear to influence raters' judgments of breathiness; however, judgments of roughness were heavily influenced by the degree of breathiness, the particular nature of the influence varying from listener to listener. Differences in how listeners focus their attention on the different aspects of multidimensional perceptual qualities apparently are a significant source of interrater unreliability (noise) in voice quality ratings.

Validity of rating scale measures of voice quality

“…Data were drawn from four previously published studies ͑Kreiman et al., 1993;Kreiman et al, 1994;Rabinov et al, 1995;Kreiman and Gerratt, 1996͒ and one unpublished study ͑Chhetri, 1997͒. Two of these studies ͑Kreiman et al., 1993;Rabinov et al, 1995͒ were specifically concerned with issues of rating reliability.…”

“…Two groups of raters participated in the studies reported in Kreiman et al ͑1994͒. The first group judged the similarity of pairs of voices with respect to breathiness or roughness.…”

“…One way to motivate scales for specific aspects of quality is with reference to overall quality: Individual scales or sets of scales may be valid to the extent that as a group they measure overall quality. For example, studies using multidimensional scaling ͑Murry et al., 1977;Kreiman et al, 1990Kreiman et al, , 1992Kreiman et al, , 1994Kempster et al, 1991;Kreiman and Gerratt, 1996͒ attempt to identify the perceptual dimensions that underlie listeners' judgments of the overall similarity of pairs of voices. Unfortunately, traditional scales have not generally emerged as perceptual dimensions from these studies, which in consequence provide little support for the validity of such scales as measures of overall vocal quality.…”

Perception of aperiodicity in pathological voice

“…͑Hillen-brand, 1988, also commented that his stimuli sounded somewhat unnatural.͒ Further, previous studies assessing the role of noise and perturbation in determining voice quality have always assessed quality in terms of specific scales like breathiness, roughness, or hoarseness. However, the reliability of such scales has been repeatedly questioned, and their validity as measures of quality is also questionable ͑e.g., Jensen, 1965;Kreiman, Gerratt, and Berke 1994;see Kreiman et al, 2005, for review͒. A final limitation of previous synthesis studies is the fact that jitter, shimmer, and noise have been manipulated independently of one another, and the perceptual interactions among these three variables have not been investigated. Acoustically, these attributes are obviously related.…”

Acoustic "breathiness measures" in the description of pathologic voices

“…Since many researchers regard "breathiness" as being caused by glottal air leakage [1,4], acoustic measures of breathiness may serve as a pool supplying useful candidates in the assessment of glottal closure. The "breathiness measure" most commonly encountered is the already mentioned H1H2 [3,[9][10][11]13]. Additionally, de Krom determined the harmonics to noise ratio (HNR) and several measures of the spectral slope as -somewhat ambiguous -best correlates of breathiness in a thorough study on the relation between acoustic measures and perceptual voice attributes [3].…”